Experimental models illustrating osmotic water transport cross liquid oil membranes have been studied and shown to be fairly semi-permeable (i.e. permeable to water and poorly permeable to KCl). Although much smaller than theoretically possible because the magnitude was limited by the model, hydrostatic heads of over 20 cm were obtained. .00275 N rubidium bromide was accumulated across a mosaic liquid ion-exchange membrane consisting of anion permselective and cation permselective parts from a .0001 N RbBr solution. This accumulation which is based on a Donnan equilibrium is 55% of the theoretical maximum for the system employed.